Agricultural machines, such as high-clearance sprayers, are getting larger and more complex to allow for increasing coverage in a single pass, which improves application efficiency. These machines often have sophisticated product delivery and other systems that are electronically controlled. Currently, sprayer starter systems have keyed starter switches and mechanical relays as safety locks to prevent starting in certain circumstances. As sprayers and their systems get more complex, there are more circumstances in which preventing starting could be beneficial, so more mechanical relays as safety locks are being implemented. However, this adds cost to the system and requires additional time for assembly. Moreover, turning the key off turns off power to electrical components. This means that the operator must shut down his controls any time he wants to start or stop his engine. This is undesirable in many circumstances, such as when using a field computer which requires loading maps, guidance lines, and so forth. A need therefore exists for an improved system which eliminates one or more of the foregoing disadvantages.